1. Field of the Invention
This invention is related in general to the field of archery and, in particular, to bowstrings and buss cables for compound bows which provide improved durability.
2. Description of the Related Art
The invention of the compound bow in 1966 was a substantial improvement in bow designs. The compound bow used a series of pulleys (or eccentrics) attached to the ends of the bow limbs. This design resulted in increased arrow velocity and reduced pull needed to hold the bow at full draw.
A problem with the compound bow is increased wear and reduced life of the bowstrings and buss cables. The increased load pressure applied to the end servings as they are bent by the eccentrics cause the end servings to separate, leaving the strings unprotected and subject to wear. The introduction of the single cam bow has exacerbated the problem. The single cam design results in even higher load pressure and bending where the high points or steep angles on the eccentric (or cam) contact the end servings.
Servings currently being used are typically made of two or more strands of material which are either twisted or braided. They are made from a variety of materials ranging from exotic aerospace materials to ordinary fishing line. The servings are applied over the bow string or buss cable in a side-by-side fashion (FIG. 1).
FIG. 1 illustrates a prior art end serving and a separation of the end serving. Bowstring 12 is protected by prior art end serving 12A. End serving 12A is made by wrapping a serving material around bowstring 12 in a side-by-side fashion. The serving material is wrapped as tightly as possible. Since the serving material is wrapped side-by-side, it is applied at nearly a 90 degree angle to bowstring 12. Even though serving material is wrapped very tightly, it is susceptible to separation 23 as bowstring 12 stretches and is subject to the high load pressure of the eccentric. Once separation occurs, the bowstring fibers are left unprotected from wear by the eccentric. The separation is unsightly and, left unprotected, bowstring 12 can become worn and break. Also shown is loop 22.
The end serving can begin to separate after only a few shots. After several more shots the serving can be separated to the point that the bowstrings or cable begin to ride directly on the eccentric and cause severe wear. The end serving is supposed to protect the strings from this type of wear.
Replacing the bowstring and cables can be costly and time consuming. Further, a broken bowstring or cable renders the bow inoperable and may even cause damage to the bow or injury to the user. The purchaser of a new bow may also assume that the manufacturer has supplied poor quality bowstring and cables on the new bow.
The prior art has attempted to solve durability problems by using new bowstring materials and/or redesigned eccentrics. An example of the prior art is illustrated by U.S. Pat. No. 4,957,094, issued Sep. 18, 1990, to Pickering et al. which is incorporated herein by reference.
Clearly there exits the need for improved bowstrings and buss cables which are durable, safer, reduce breakage and resist unsightly separation.